1. Field of the Invention
The present invention relates to an optical recording medium processing apparatus for optically recording information to and/or reproducing information from an optical recording medium, such as a magneto-optical disk, and in particular to an optical recording medium processing apparatus performing a seek control process without a sensor for detecting the position of a carriage for moving a light beam spot in direction extending across the tracks of the recording medium.
2. Related Arts
One of the presently available optical recording mediums is the magneto-optical disk. Such a disk is composed of a substrate and of a magnetic recording layer which is deposited on the substrate. To record information on a magneto-optical disk, optical heating and magnetic field changes are employed. To reproduce information which has been recorded on a magneto-optical disk, magneto-optical technology is employed. On a magneto-optical disk there are data tracks for recording data and control tracks for recording medium information unique to the magneto-optical disk, and included in each track is an identification (ID) portion for identifying a sector as a recording area, and a data portion for recording data. In order to prevent the overwriting of data, the control track is provided by using a stamper to form embossed bits in the substrate. The embossed bits in the substrate can also be formed by injection molding. For the same reason, embossed bits also formed in the substrate in the identification portion using the same manufacturing process.
Currently available magneto-optical disks have several different memory capacities, 128 MB, 230 MB, 540 MB, 640 MB and 1.3 GB. The PPM (Pit Position Modulation) recording method for recording data in accordance with whether a mark is present on the disk is employed for a magneto-optical disk of 128 MB. Constant angular velocity (CAV) is employed as the recording formatting for a magneto-optical disk of 128 MB, and zone constant angular velocity (ZCAV) is employed for a magneto-optical disk of 230 MB. In a user area on a magneto-optical disk of 128 MB there is one zone, whereas in a user area on a magneto-optical disk of 230 MB there are ten.
The PWM (Pulse Width Modulation) recording method for recording data while correlating with the edges of a mark, i.e., the front edge and the rear edge, is employed for the high-density recording of MO cartridge media having capacities of 540 MB and 640 MB. This difference in the memory capacities of the 540 MB and the 640 MB magneto-optical disks is due to a difference in sector capacities. When a sector capacity of 2048 bytes is employed, an optical disk of 640 MB is produced, but when a sector capacity of 512 bytes is employed, an optical disk of 540 MB is produced. The recording format used for both optical disks is zone CAV, but in a user area on an optical disk of 640 MB there are 11 zones, while in a user area on an optical disk of 540 MB there are 18 zone.
As is described above, since the data recording methods, the recording formats and the sector capacities differ depending on the capacities of the several types of magneto-optical disks, to cope with these disks which have such different specifications, an optical recording medium processing apparatus for storing data on, or for reproducing data stored on a magneto-optical disk must also be capable of identifying the recording media type at the time a magneto-optical disk is loaded.
Conventionally, the ID portion of a track is read from a location near the center, between an inner circumferential position and an outer circumferential position, of a magneto-optical disk which has been loaded, and bit interval is employed to identify the magneto-optical disk type. For the identification of the magneto-optical disk type, the bit interval in the ID portion at the location near the center is employed because if the bit interval in an ID portion near the inner circumferential position or the outer circumferential position were used, an erroneous identification would be obtained.
In order to read the ID portion of a track near the center of a magneto-optical disk, when a magneto-optical disk is loaded the optical recording medium processing apparatus performs an initial process, i.e., an initial seek control process, for moving a carriage including a lens to guide a light beam to the face of the magneto-optical disk in the direction extending across the tracks, and for positioning the light beam at a track near the center of the recording medium.
Since when a magneto-optical disk is loaded or when the power is turned on the position of the carriage is unknown, the optical recording medium processing apparatus need to recognize the position of the carriage in the direction extending across the tracks. Thus, when a magneto-optical disk is loaded, a predetermined current is supplied to a coil for driving the carriage, and the carriage is first impelled inward until it arrives at the innermost circumferential position. Even if the carriage is located at the outermost circumferential position when a magneto-optical disk is loaded, a predetermined current, which is adequate as far as strength or time is concerned, is supplied to impel the carriage until it arrives at the innermost circumferential position.
Included in a conventional optical recording medium processing apparatus is a position sensor which is turned on when the carriage is situated at the innermost circumferential position, and is turned off when the carriage moves a predetermined distance from the innermost circumferential position to the direction extending across the tracks. That is, the optical recording medium processing apparatus recognizes that the carriage is located at the innermost circumferential position by the turning-on of the position sensor, the apparatus can then control moving the carriage based on the recognition. Subsequently, when the carriage is moved and the light beam spot is positioned on near the center of the recording medium, the light beam can be focused and various other adjustments can be made.
However, since the position sensor is included in the optical recording medium processing apparatus, manufacturing costs are increased.
It is, therefore, one objective of the present invention to provide an optical recording processing apparatus performing an initial seek control process for a carriage without the position sensor.
To achieve the above objective, according to the present invention, there is provided an optical recording medium processing apparatus for accessing the recording medium by irradiating a light beam to a recording medium comprising:
a carriage including a lens to guide the light beam to the recording medium for moving in a direction extending across tracks on the recording medium;
a detector for detecting a tracking error signal indicating a difference between a predetermined track and a light beam spot on the recording medium; and
a controller for moving the carriage across the tracks from an innermost circumferential position of the recording medium or the vicinity of the position, for counting the number of tracks in accordance with a track zero-cross pulse generated by a tracking error signal having a predetermined level or higher detected by the detector, and after the carriage has been moved for a predetermined period of time, for positioning the light beam spot on a target track in accordance with the counted number of the tracks.
As a result, when a recording medium is loaded, or when power is turned on, the initial seek control process, whereby the carriage is moved from the innermost circumferential position of the recording medium or its vicinity to the center, can be performed without a position sensor being required.
The detector detects the tracking error signal from a track area including tracks standardized by a predetermined standard on the recording medium, after the carriage has been moved for the predetermined period of time. Therefore, the light beam spot can be positioned on a target track that is designated in advance, by counting the number of tracks encountered before the target track is reached.
The controller accelerates the carriage for a predetermined period of time, and then moves the carriage at a predetermined constant speed. During the constant speed control, the amplitude level for a tracking error signal and an offset are adjusted. Therefore, at the same time as the light beam spot is positioned near the center of the recording medium, track-on control can be started.